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document type_implements_trait #132608

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Nov 5, 2024
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document type_implements_trait #132608

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c88ba28
document `type_implements_trait`
mejrs Nov 4, 2024
e37a3a8
Explain how to evaluate an obligation
mejrs Nov 5, 2024
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12 changes: 12 additions & 0 deletions compiler/rustc_trait_selection/src/infer.rs
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Expand Up @@ -60,6 +60,18 @@ impl<'tcx> InferCtxt<'tcx> {
///
/// Invokes `evaluate_obligation`, so in the event that evaluating
/// `Ty: Trait` causes overflow, EvaluatedToAmbigStackDependent will be returned.
///
/// `type_implements_trait` is a convenience function for simple cases like
///
/// ```ignore (illustrative)
/// let copy_trait = infcx.tcx.require_lang_item(LangItem::Copy, span);
/// let implements_copy = infcx.type_implements_trait(copy_trait, [ty], param_env)
/// .must_apply_modulo_regions();
/// ```
///
/// In most cases you should instead create an [Obligation](traits::Obligation)
/// and check whether it holds, because it properly handles higher ranked traits
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Suggested change
/// and check whether it holds, because it properly handles higher ranked traits
/// and check whether it holds via `evaluate_obligation` or one of its helper functions like `predicate_must_hold_modulo_regions`, because it properly handles higher ranked traits

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perhaps

/// and it is more convenient and safer when your `params` are inside a `Binder`.
#[instrument(level = "debug", skip(self, params), ret)]
fn type_implements_trait(
&self,
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